Update JSONReader to take base::StringPiece instead of std::string

base/json/json_reader.h

Index: base/json/json_reader.h
diff --git a/base/json/json_reader.h b/base/json/json_reader.h
index e0811754b1957f36a4cd01b462aa835810671f25..a11102f0036e28baa8c32cd50368655826f0165c 100644
--- a/base/json/json_reader.h
+++ b/base/json/json_reader.h
@@ -33,6 +33,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/string_piece.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
@@ -95,18 +96,18 @@ class BASE_EXPORT JSONReader {
 
   // Reads and parses |json|, returning a Value. The caller owns the returned
   // instance. If |json| is not a properly formed JSON string, returns NULL.
-  static Value* Read(const std::string& json);
+  static Value* Read(const StringPiece& json);
 
   // Reads and parses |json|, returning a Value owned by the caller. The
   // parser respects the given |options|. If the input is not properly formed,
   // returns NULL.
-  static Value* Read(const std::string& json, int options);
+  static Value* Read(const StringPiece& json, int options);
 
   // Reads and parses |json| like Read(). |error_code_out| and |error_msg_out|
   // are optional. If specified and NULL is returned, they will be populated
   // an error code and a formatted error message (including error location if
   // appropriate). Otherwise, they will be unmodified.
-  static Value* ReadAndReturnError(const std::string& json,
+  static Value* ReadAndReturnError(const StringPiece& json,
                                    int options,  // JSONParserOptions
                                    int* error_code_out,
                                    std::string* error_msg_out);